Conventionally, a vehicle (namely, four-wheel-drive vehicle) includes a torque distributor for distributing a torque of power generated in a power source such as an engine to main driving wheels and auxiliary driving wheels. In this kind of vehicle, for example, with the main driving wheels and the auxiliary driving wheels being respectively front wheels and rear wheels, the torque of power generated in the power source is transmitted to the front wheels via a front drive shaft and a front differential and also to the torque distributor provided with a hydraulic multidisc-type clutch via a propeller shaft. And, by supplying hydraulic fluid at a predetermined pressure to the torque distributor from a hydraulic control device, an engagement pressure of the torque distributor is controlled. Thus, the torque of power from the power source is transmitted to the rear wheels at a predetermined distribution ratio. For example, refer to Patent Document 1.
In the calculation of a torque distribution (namely, command torque) distributed to the rear wheels with respect to the front wheels in the control device for the torque distributor, a rear wheel basic distribution torque serving as a base torque of the command torque is calculated from data such as a load ratio of the rear wheels with respect to the front wheels and an estimated driving force. And, the torque distribution (command torque) to the rear wheels with respect to the front wheels is determined on the basis of this rear wheel basic distribution torque.